Field of the invention
The present invention relates to an apparatus and a method for manufacturing a composite membrane, such as a catalyst-coated membrane for a fuel cell, having a functional layer formed on a band-like thin film.
Description of the Background Art
In recent years, fuel cells have been garnering attention as drive power sources for automobiles, household uses, mobile phones and the like. A fuel cell is a power generation system that generates electric power through electrochemical reaction between hydrogen (H2) contained in the fuel and oxygen (O2) in the air, and is characterized by high power generation efficiency and low environmental load.
There are several types of fuel cells that vary according to the electrolytes used. One of them is a polymer electrolyte fuel cell (PEFC) that uses an ion-exchange membrane (electrolyte membrane) as the electrolyte. PEFCs are capable of operating at room temperature and can be reduced in size and weight, and therefore, they are expected to be applied to automobiles and portable devices.
A catalyst-coated membrane (CCM) used for a polymer electrolyte fuel cell is a composite membrane having catalyst layers formed on both sides of a thin film of an electrolyte as functional layers. A gas diffusion layer and a separator are disposed on the opposite sides of the catalyst-coated membrane, and thereby, a unit cell is formed. Such a catalyst-coated membrane is made by applying, to the surface of the electrolyte membrane, an electrode ink (electrode paste) obtained by dispersing a catalyst containing platinum (Pt) in a solvent such as alcohol. However, the electrolyte membrane has the tendency of undergoing swelling and shrinkage by easily absorbing the solvent contained in the electrode ink and moisture in the atmosphere. This has posed a problem in that creases and pinholes are generated in the electrolyte membrane at the time of applying and drying the electrode ink. Generation of creases and pinholes in the electrolyte membrane leads to a reduction in the power generation performance of the fuel cell.
To solve such a problem, Japanese Patent Application Laid-Open - No. 2001-70863 discloses a technique for transporting an electrolyte membrane while sucking the electrolyte membrane using a suction heating roller, and immediately heating and drying the electrode ink applied to the electrolyte membrane, thereby inhibiting deformation of the electrolyte membrane. Additionally, US2007/0190253 discloses a technique for spray applying an electrode ink to an electrolyte membrane that is sucked on a roller, and drying the electrode ink by heating with a roller. Furthermore, Japanese Patent Application Laid-Open No. 2011-165460 discloses suspending an electrolyte membrane having a shape-retaining film attached to its one side on a backup roller, applying a catalyst ink onto the other side of the electrolyte membrane, and also attaching a shape-retaining film to the other side of the electrolyte membrane on which a catalyst layer has been formed after the catalyst ink was dried, thereby preventing creases from being generated in the electrolyte membrane.
However, with the techniques disclosed in Japanese Patent Application Laid-Open No. 2001-70863 and US2007/0190253, the electrode ink is applied, with the electrolyte membrane being sucked by the roller. Accordingly, although it is possible to prevent deformation due to swelling of the electrolyte membrane during coating, there is the possibility that the electrolyte membrane may undergo swelling and shrinkage caused by the absorption of the solvent of the electrode ink and the drying of the ink when the electrolyte membrane is separated from the roller after coating. Moreover, with the technique disclosed in Japanese Patent Application Laid-Open No. 2011-165460, the electrolyte membrane is simply suspended on the backup roller, and therefore, there is the possibility that the electrolyte membrane may be displaced from the shape-retaining film during coating in the case of applying an electrode ink using a solvent that undergoes a significant degree of swelling. That is, in any case, there is the possibility that the electrolyte membrane may undergo deformation during manufacture of the catalyst-coated membrane.